Fluid deionization system

ABSTRACT

A staged or serial deionization system is described. The system includes N deionization subsystems. The system has a charging state for deionizing fluid and a discharging state for deionizing the respective deionization subsystem. In the charging state, ionized fluid is discharged serially. In the discharging state, N deionization subsystems are discharged in parallel, thereby reducing the ecological impact of the discharge brine.

RELATED APPLICATIONS

[0001] The present invention claims priority to U.S. Provisional PatentApplication No. 60/421,320 filed on Oct. 25, 2002, which is incorporatedby reference herein.

BACKGROUND

[0002] Deionized water is employed in many commercial applications, suchas semiconductor and chrome-plating plants, automobile factories,beverage production, and steel processing. Further, systems arecontemplated in homes units, businesses, manufacturing and municipalfacilities, and other applications that can recycle their water output,cutting costs and protecting the environment.

[0003] Of course, a prime objective of flow through capacitor technologyentails the desalinization of sea water at a reasonable cost, providingan inexhaustible supply of usable water to regions in need. Presently,advanced research is underway using new materials including carbonnanotubes.

[0004] Nonetheless, the water demands of the Third World are immediate.Two-thirds of the world population do not have access to clean water.Most disease in the developing world is water-related—more than 5million people a year die of easily preventable waterborne diseases suchas diarrhea, dysentery and cholera.

[0005] Plainly stated, potable water will be the most valuable commodityin the future. The world's population will double in the 50 to 90 years.Per capita water consumption increases while the supply deteriorates.80% of the world's population lives within 200 miles of a coastlinewhere water is available but not potable or suitable for agriculture.70% of the ground water is brackish. 85% of all illness is associatedwith unsafe drinking water.

[0006] Flow through capacitors have been developed to separate materialsfrom fluid streams, such as salt from water. For example, Andleman U.S.Pat. Nos. 5,192,432, 5,186,115, 5,200,068, 5,360,540, 5,415,768,5,547,581, 5,620,597, 5,415,768, and U.S. Pat. No. 5,538,611 to ToshiroOtowa, all of which are incorporated by reference herein, describe flowthrough capacitor systems which filters polluted and brackish waterbetween alternating electrodes of activated carbon (the capacitors).Further, Faris PCT Application No. US02/25076 filed on Aug. 7, 2002entitled “Movable Electrode Flow-Through Capacitor” and Faris et al. PCTApplication No. US03/26693 filed on Aug. 26, 2003 entitled “FluidDesalinization Flow Through Capacitor Systems”, both of which areincorporated herein by reference in their entireties, describe flowthrough capacitor systems with improved throughput. In general, whenvoltage is applied, salts, nitrates, totally dissolved solids and otheradulterants in the water are attracted to the high surface area carbonmaterial. Solids develop on the electrodes, and thus the process must bestopped to remove the contaminants as concentrated liquid. This isaccomplished by short-circuiting of the electrodes.

[0007] This method has been taught as a better process for waterdesalinization than traditional systems like reverse osmosis, whichpasses through contaminants such as nitrates, promotes bacterial growthand wastes one or more gallons of water for every one it purifies.Further, ion exchange systems, also widely used, generate pollution anduse strong acids, bases and salts to regenerate the resin.

[0008] However, limited lifetime of the electrodes results in highcapital costs, and electrodes must be frequently replaced. Complexelectrode support structures, intra-electrode and inter-electrodeplumbing, and housings are difficult to recover from conventional flowthrough capacitor systems.

[0009] Further, another drawback of many conventional flow throughcapacitor and other deionization systems, particularly for economicalwater desalination, is the high concentrations of the discharged brine.It is not uncommon for conventional water desalinization plants todischarge brine directly into the ocean. This brine may haveconcentration up to and even greater then twice that of seawater. Thiscreates unnatural regions of high salt concentration seawater,disrupting the ecological system. Thus, while achieving necessary goalsof providing potable water to municipalities and a water source forirrigation, the unintended environmental and ecological impacts ofconventional desalination plants and systems may ultimately outweigh theintended results.

[0010] Therefore, it is desirable to provide a relatively ecologicallybenign system and process to desalinate water, or to remove othersubstances from a material, as is needed.

SUMMARY

[0011] The above-discussed and other problems and deficiencies of theprior art are overcome or alleviated by the several methods andapparatus of the present invention for removing ionic substances fromfluids, such as removing salt from water.

[0012] A staged or serial deionization system is described. The systemincludes N deionization subsystems (e.g., flow through capacitors). Thesystem has a charging state for deionizing fluid and a discharging statefor deionizing the respective deionization subsystem. In the chargingstate, input ionized fluid having an ion concentration C is introducedin an Nth deionization subsystem for decreasing the concentration of thefluid by Δ_(N), resulting in a fluid stream having a concentrationC−Δ_(N). The C−Δ_(N) fluid stream is inputted to a subsequentdeionization subsystem and is charged therein by decreasing theconcentration of the fluid by Δ_(N). The process ultimately provides anoutput fluid stream having a concentration C−$\sum\limits_{k = 1}^{N}{\Delta_{k}.}$

[0013] To discharge the system, in certain preferred embodiments, thesystem is electrically shorted, and flush fluid having a concentration Fis flushed in parallel through the N deionization subsystems.Accordingly, the maximum concentration of the brine (discharged fluid)is F+Δ_(M), where ΔM is the largest value of the values ΔN. This isparticularly advantageous over conventional systems that would discharge$C - {\sum\limits_{k = 1}^{N}{\Delta_{k}.}}$

[0014] For example, if all of the values ΔN are approximately equal (Δ),and the flush fluid is the same inlet fluid to be deionized (F=C), thenthe discharge fluid from N subsystems would be approximately C−Δ, asopposed to conventional systems having discharge fluid concentrations ofC−NΔ.

[0015] The above-discussed and other features and advantages of thepresent invention will be appreciated and understood by those skilled inthe art from the following detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a schematic representation of a serial deionizationsystem having parallel discharge mode; and

[0017] FIGS. 2A-2C depict another serial deionization system and modesof operation.

DETAILED DESCRIPTION

[0018] Herein disclosed is a serial deionization system. The serialdeionization system allows for a system configuration that is modular,scaleable, rapidly deionizing, and efficient.

[0019] Referring to FIG. 1, a system 100 for de-ionizing a fluid isdescribed. The system 100 includes a plurality of deionizationsubsystems 10, 20, 30 . . . N, such as flow through capacitors. Threeare shown for convenience, thus it is intended that any number from 2 toN may be used in the system, wherein N may be as few as 2 and as many asneeded for the application (e.g., 10s, 100s, 1000s).

[0020] The flow through capacitors are electrically connected to a powersource, and the power connection is configured to alternate, forexample, for alternating charging functions (e.g., deionizing fluidflowing through flow through capacitors) or discharging functions (e.g.,deionizing collected ions from flow through capacitors). The powersource may be DC or AC. In DC operations, the polarities may be reversedto switch between charging and discharging. In AC operations, forexample, phases may be alternated to vary charging and dischargingcycles.

[0021] During charging (fluid deionization) operations, ionized fluidhaving a concentration C is introduced via a stream 2 into the firstdeionization subsystem (e.g., flow through capacitor) 10. A valve 5 isin the “off” position, to prevent fluid with concentration C fromentering deionization subsystems 20, 30, . . . N. A valveI_(C20)/O_(D10) is configured to allow flow to into the seconddeionization subsystem (e.g., flow through capacitor) 20. A valveI_(C30)/O_(D20) is configured to allow flow to into the thirddeionization subsystem (e.g., flow through capacitor) 30, and so on forN deionization systems. The deionization subsystems 10, 20, 30 . . . Neach decreases the concentration of the respective incoming fluid streamby a value Δ₁₀, Δ₂₀, Δ₃₀, . . . Δ_(N), wherein Δ₁₀, Δ₂₀, Δ₃₀, . . .Δ_(N) may each be the same or different. Therefore, the deionized fluidstream 50 has a concentration C−(Δ₁₀+Δ₂₀+Δ₃₀+ . . . Δ_(N)), andaccordingly, if Δ₁₀, Δ₂₀, Δ₃₀, Δ_(N) are the same, the deionized fluidstream 50 has a concentration C−NΔ.

[0022] In other terms, a system including N deionization subsystems,each decreasing the concentration of the fluid (having an initial ionconcentration of C) by Δ_(N), a deionized output fluid stream resultshaving a concentration $C - {\sum\limits_{k = 1}^{N}{\Delta_{k}.}}$

[0023] In the discharging state (deionization system deionization), asshown in the example of FIG. 1, each system 10, 20, 30 . . . N receivesan input from input stream 2, wherein valve 5 is open. The output valvesfor each subsystem 10, 20, 30 . . . N are configured to allow ionizedfluid to exit via outlets 60.

[0024] A key benefit to the system of FIG. 1, referred to as “seriescharge/parallel discharge”, is that the discharge product only has aconcentration in the range of C+Δ, which is environmentally safe, ascompared to conventional deionization system outputs or brine dischargeproducts.

[0025] In other terms, discharge of N cells using flush fluid having aconcentration F results in maximum brine (discharged fluid)concentrations of F+Δ_(M), where ΔM is the largest value of the valuesΔN. This is particularly advantageous over conventional systems thatwould discharge $C - {\sum\limits_{k = 1}^{N}{\Delta_{k}.}}$

[0026] The deionization subsystem, in the embodiment of FIG. 1 and inother embodiments herein, may comprise any known reverse osmosis system,ion exchange system, flow through capacitor system, or combinationthereof. In certain preferred embodiments, a flow through capacitorsystem is used. Typical flow through capacitor systems include a pair ofelectrodes having a space therebetween for fluid flow. Upon applicationof a voltage (e.g., from a DC source, and contacting the electrodes viasuitable contacts) and passage of an ionic fluid, ions of appropriatecharge are attracted to the electrodes, forming an electric doublelayer.

[0027] A high surface area conductive constituent alone may be formed asthe electrodes, or may be supported on appropriate substrates(conductive or non-conductive, depending on the form of the electrodes).Alternatively, a current collector and a high surface area conductiveconstituent may be in the form of layers, or may be a single layer, forexample, as described in An exemplary air cathode is disclosed in U.S.Pat. No. 6,368,751, entitled “Electrochemical Electrode For Fuel Cell”,to Wayne Yao and Tsepin Tsai, filed on Oct. 8, 1999, which isincorporated herein by reference in its entirety.

[0028] The high surface area conductive material employed in theflow-through capacitor may comprise a wide variety of electricallyconductive materials, including, but not limited to, graphite, activatedcarbon particles, activated carbon fibers, activated carbon particlesformed integrally with a binder material, woven activated carbon fibroussheets, woven activated carbon fibrous cloths, non-woven activatedcarbon fibrous sheets, non-woven activated carbon fibrous cloths;compressed activated carbon particles, compressed activated carbonparticles fibers; azite, metal electrically conductive particles, metalelectrically conductive fibers, acetylene black, noble metals, noblemetal plated materials, fullerenes, conductive ceramics, conductivepolymers, or any combination comprising at least one of the foregoing.The high surface area material may optionally include coatings orplating treatments with a conductive material, such as palladium,platinum series black, to enhance electrical conductivity. The highsurface area material may also be treated with chemicals such as alkali,e.g., potassium hydroxide, or a halogen, e.g., fluorine; to increase thesurface area and conductivity. Activated carbon material of greater thanabout 1000 square meters per gram surface area are preferred, but it isunderstood that lower surface area materials may also be employed,depending on factors including but not limited to the distance betweenthe electrodes, the voltage applied, the desired degree of ion removal,the speed of the movable cathodes, and the configuration of the movablecathodes.

[0029] Referring now to FIGS. 2A-2C, a staged or serial deionizationsystem is depicted. The system includes N flow through capacitors 110,120, 130 . . . N electrically connected to a suitable power supply in acharging state for deionizing fluid and electrically shorted in adischarging state for deionizing the respective flow through capacitor.

[0030] In the charging state, as shown in FIG. 2B, input ionized fluidhaving an ion concentration C is introduced in the flow throughcapacitor 110, wherein the concentration of the fluid is decreased by Δ1to a fluid stream having a concentration C−Δ1. The C−Δ1− fluid stream isinputted to flow through capacitor 120 and is charged therein bydecreasing the concentration of the fluid by Δ2 to a deionized outputfluid stream having a concentration C−Δ1−Δ2. Likewise, the C−Δ1−Δ2−Δ3fluid stream is inputted to flow through capacitor 130 and is chargedtherein by decreasing the concentration of the fluid by Δ3 to adeionized output fluid stream having a concentration C−Δ1−Δ2−Δ3. Notethat the Δ values may be the same or different, as described above.

[0031] In the discharging state, and referring now to FIG. 2C, adischarging input fluid having concentration F is inputted in parallelto the flow through capacitors 110, 120, 130. Output fluid from the flowthrough capacitors 110, 120, 130 having a concentration F+Δ1, F+Δ2, F+Δ3is discharged from the system. Such a system is ecologically benign,especially compared to conventional systems that would discharge fluidhaving a concentration F+Δ1+Δ2+Δ3+ΔN.

[0032] In one preferred embodiment, the valving and plumbing arrangementis constructed to be reuseable, wherein the deionization units or flowthrough capacitors 110, 120, 130 (or 10, 20, 30) are modular andreplaceable.

[0033] While preferred embodiments have been shown and described,various modifications and substitutions may be made thereto withoutdeparting from the spirit and scope of the invention. Accordingly, it isto be understood that the present invention has been described by way ofillustrations and not limitation.

What is claimed is:
 1. A staged deionization system comprising: a firstand second deionization subsystems having a charging state fordeionizing fluid and a discharging state for deionizing the respectivedeionization subsystems, wherein in the charging state, input ionizedfluid having an ion concentration C is introduced in the firstdeionization subsystem wherein the concentration of the fluid isdecreased by Δ₁ to a fluid stream having a concentration C−Δ₁, and theC−Δ₁ fluid stream is introduced to the second deionization subsystem andis charged in second deionization subsystem by decreasing theconcentration of the fluid by Δ₂ to a deionized output fluid streamhaving a concentration C−(Δ₁+Δ₂), and wherein in the discharging state,flush fluid is inputted in parallel to the first deionization subsystemand second deionization subsystem, wherein ions that have built up inthe first deionization subsystem and second deionization subsystem aredischarged.
 2. A staged deionization system comprising: N deionizationsubsystems represented by k=1 through N, each having a charging statefor deionizing fluid and a discharging state for deionizing therespective deionization subsystem, wherein in the charging state, Nserially connected systems each decrease the concentration of inputfluid initially having a concentration C by an amount of Δ_(k) at eachstage resulting in an output deionized fluid stream having aconcentration ${C - {\sum\limits_{k = 1}^{N}\Delta_{k}}},$

and wherein in the discharging state, the N deionization subsystems areflushed in parallel with flush fluid having a concentration F, resultingin maximum discharged fluid concentrations of F+Δ_(M), where ΔM is thelargest value of the values Δk.
 3. The staged deionization system as inone of claims 1 or 2, wherein at least one of the deionizationsub-systems comprise flow through capacitors electrically connected toan electrical connection in the charging state and electrically shortedin the discharging state.
 4. The staged deionization system as in one ofclaims 1 or 2, wherein fluid communication between input fluids,deionization systems, flush fluids, and discharge fluids is provided inthe form of plumbing and valves configured and constructed to bereusable, and wherein the deionization systems are modular.